[clug] IPv6 for home

Michael Still mikal at stillhq.com
Sat Dec 31 18:52:39 MST 2011

Hash: SHA1

On 30/12/11 13:39, Paul Wayper wrote:
> On 12/30/2011 11:44 AM, Michael Still wrote:
>> Dear Internet. I am confused by your new fangled IPv6.
>> Personally, I think we should have jumped to IPv8, but I was
>> overruled on that. So, given the current schmozzle we find
>> ourselves in, please advise:
> Congratulations to Scott Ferguson for writing an amusing reply.
> I'm going to go rad and be serious for a change :-)

Thanks everyone for their replies so far...

>> - I have a DSL modem. Because Telstra are evil, it only gets
>> 3.3mbit to the Internet, but that doesn't seem relevant. However,
>> it does claim to get an IPv6 address, which is exciting.
> If it's not an FE80::/16 address - most likely something in the
> 2001::/16 range - then you're good to go.  IPv6 has the concept of
> different address ranges covering the same machine, usually for
> different networks.  FE80::/16 are 'link-local' addresses randomly
> decided by the network stack that are only supposed to work on the
> local network.

Yeah, the address is 2001:44b8:... on the modem, so I think that means
the modem has a routable IP.

> So you've got a gateway; so far so good.  That bit took me a
> while.
>> - I have a machine on the network (not the DSL modem) which hands
>> out IPv4 DHCP leases, as well as acting as a DNS server.
> I'm assuming from your description that that machine isn't the same
> as your router with the IPv6 address.  That's OK, as I understand
> it.


>> I'd like IPv6 to just magically work for the home network, and be
>> able to route packets to the Internets. I'd also like to keep DNS
>> resolution going via the home DNS server if possible, as DNS
>> latency is a big performance problem for me.
>> So, how should I do that?
>> - Should I run a DHCPv6 server on the DHCP machine? Does that
>> really mean running two copies of ISC dhcpd?
> Yes, sadly, because AFAICS there's two versions of dhcpd.
> Alternately, you can run a route advertising daemon (radvd) on your
> DHCP/DNS server.  It looks out for IPv6 "what are the local route?"
> packets and replies with "you can pick one in this range, and the
> router is this address" responses.  If the gateway and the radvd
> server are the same machine, then the config is easier, but there's
> no reason why they can't be separate AFAICS.
>> - Should I obtain an address range for use in my house, or should
>> I just use the netblock Internode hands my modem?
> You've already got one, it should be right to go.

Yeah, I think I wasn't clear here though. Is there any tangible
advantage to going and getting a netblock assigned to my house? Is it
exciting in some way I can't imagine to have each machine on the
network have an permanent externally routable IP?

>> Please do my homework for me. I'm obsessed with the desire to
>> experience animated turtles, but not obsessed enough to have done
>> any research at all.
> OK, install radvd and set up an /etc/radvd.conf file looking
> something like this:
> interface eth0 { AdvSendAdvert on; prefix 2001:mika:lsip:rnge::/64 
> { AdvOnLink on; AdvAutonomous on; }; };
> Your homework is to work out what bits to change and, possibly,
> what I've left out.  Steve Walsh may be able to help there too :-)

For reference, the LAN netblock is provided by internode at

So, I did this. The interface on the DNS / DHCP machine now has a
reasonable looking IPv6 address. However, there are no IPv6 routes on
the machine that I can see. In fact, if I ping6 the external IP for
the DSL modem, I get told the "network is unreachable".

External brain -- please think more for me.

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